Date of Award

Winter 2003

Document Type


Degree Name

Doctor of Philosophy (PhD)


Aerospace Engineering

Committee Director

Colin P. Britcher

Committee Member

Drew Landman

Committee Member

Ponnampalam Balakumar

Committee Member

Halima Ali

Committee Member

Oktay Baysal


The results of a wind tunnel experiment are reported, which investigated two different flow control techniques that demonstrated the potential of increasing the lift coefficient on a multi-element airfoil. The data also indicated that boundary-layer separation on the trailing-edge flap could be reduced significantly. Results of the investigation revealed that for some test conditions an increased amount of suction occurred on the upper surface of the main element where the flow was attached. One of the techniques that was tested in this investigation involved the use of a pair of piezoelectric devices attached to the model to provide oscillatory motion directly to the flow field of the airfoil. The other technique employed a loudspeaker, which was mounted on the wall of the test section to supply acoustic excitation to the surrounding flow field. During the primary portion of the test, the free stream velocity in the test section was 20 m/s and the model attitude was fixed at 19° angle of attack. The piezoelectric devices were operated at frequencies of 0, 80, 90, 100, and 120, 240, 260 and 320 Hz. The loudspeaker was operated at only two frequencies of 80 and 120 Hz. Velocity profiles were obtained using a TSI® hot-film sensor and anemometer. These velocity profiles were measured on the main element and on the trailing-edge flap. The data showed that increments in mean velocity profile were achieved on the separated trailing-edge flap when the piezoelectric devices were driven at frequencies of 100 and 120 Hz at 19° angle of attack. When the model was tested at 15° angle of attack, the largest increase in lift was achieved when the devices were driven at 320 Hz. The largest increment in lift occurred when the flow field was acoustically excited at 80 Hz. Linear Stability Analysis was employed to predict the vortex passage frequency behind the slat.